Annular optical device

ABSTRACT

One embodiment provides an annular optical device ( 100 ), comprising: an annular meso-optic ( 1 ) including an annulus ( 11 ) centered about an axis of revolution (A); and a secondary optical structure ( 2 ) substantially coaxial within the annulus ( 11 ) of the annular meso-optic ( 1 ), wherein the secondary optical structure ( 2 ) and the annular meso-optic ( 1 ) are separated by a media ( 12 ) comprising a media refractive index that is lower than a secondary optical structure refractive index, with the secondary optical structure ( 2 ) being configured to hold a specimen to be radiated by impinging electromagnetic radiation directed into the secondary optical structure ( 2 ) substantially along the axis of revolution (A), wherein re-directed radiation from the specimen is allowed into the annular meso-optic ( 1 ) by the secondary optical structure ( 2 ) if an angle of incidence of the re-directed radiation exceeds the angle of Total Internal Reflectance. Other embodiments are descried and claimed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/814,669, which is a national phase entry of PCT/US2011/46105, whichis a non provisional of 61/371,381 filed 2010-08-06, the contents ofeach which are hereby incorporated by reference, and a continuation inpart of co-pending U.S. application Ser. No. 13/395,153 filed2012-03-09, which is national phase application of internationalapplication PCT/US2010/048091 filed 2010-09-08, which is a nonprovisional of 61241654 filed 2009-09-11, the contents of each which arehereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to an optical device, and moreparticularly, to an annular optical device.

BACKGROUND OF THE INVENTION

A difficulty is found in the measurement of weak electromagneticradiation, such as optical radiation or electromagnetic radiation ofwavelengths of about 0.01 to 1000 micrometers (um). Such weak radiationmay comprise the light produced by the emission of a fluorescent orluminescent specimen or the reflectance signal of a particle in asuspension media as in the measure of a turbid specimen for thedetermination of concentration.

In such circumstances, a difficulty is in the discrimination between theinherent noise of a detection system and the signal value produced bythe specimen. The Signal to Noise Ratio (SNR) is a measure of signalvalue relative to the noise value of a detection system. In practice, asignal value approximately twice the noise value is considered apractical limit of a detection system for discriminating with confidencethe signal value from the noise value.

Various methods can be employed to reduce inherent noise value of adetection system, such as cooling of the detector to reduce the thermalgeneration of random electrons or by employing signal processingtechniques such as signal averaging. But these methods are limited inapplication or effectiveness, wherein a limit is reached wherein littleor no further reduction of the noise value can be achieved by signalprocessing.

If the noise value of the detector cannot be further reduced, thenimprovements to the SNR can only be achieved through increases in thesignal value. One common method employed to improve the signal value isto concentrate the radiation onto the detector. Another method is toincrease the intensity of the stimulating radiation. However, increasingthe intensity of the stimulating beam may result in damage of thespecimen due to heating or breaking of molecular bonds, and is thereforelimited to some threshold of practicality.

Conventional optical elements for the concentration of opticalradiation, such as lenses or mirrors, are directional in nature,collecting radiation emitted along a specific ray path from a specificdirection or area of origin. Typically, systems utilized in thedetection of weak optical signals are positioned substantiallyperpendicularly to the incident beam of stimulating radiation so as tomaximize the SNR. Additionally, much of the radiation emitted byfluorescence or particle scatter goes undetected as consequence of afinite subtended angle of the radiation concentrator device.

Another source of noise which can affect the SNR of an opticalmeasurement system is stray radiation. Stray radiation is detectableradiation which impinges upon the detection device, generating a signalunrelated to the specimen or electromagnetic phenomenon underexamination. As an example, radiation which is received in the detector,but which did not propagate through or interact with the sample, is acommon stray radiation.

SUMMARY OF THE INVENTION

One embodiment provides an annular optical device (100), comprising: anannular meso-optic (1) including an annulus (11) centered about an axisof revolution (A); and a secondary optical structure (2) substantiallycoaxial within the annulus (11) of the annular meso-optic (1), whereinthe secondary optical structure (2) and the annular meso-optic (1) areseparated by a media (12) comprising a media refractive index that islower than a secondary optical structure refractive index, with thesecondary optical structure (2) being configured to hold a specimen tobe radiated by impinging electromagnetic radiation directed into thesecondary optical structure (2) substantially along the axis ofrevolution (A), wherein re-directed radiation from the specimen isallowed into the annular meso-optic (1) by the secondary opticalstructure (2) if an angle of incidence of the re-directed radiationexceeds the angle of Total Internal Reflectance.

Another embodiment provides a method of forming an annular opticaldevice, the method comprising: providing an annular meso-optic includingan annulus centered about an axis of revolution; and providing asecondary optical structure substantially coaxial within the annulus ofthe annular meso-optic, wherein the secondary optical structure and theannular meso-optic are separated by a media having a media refractiveindex that is lower than the refractive index of the secondary opticalstructure, with the secondary optical structure being configured to holda specimen to be radiated by impinging electromagnetic radiationdirected into the secondary optical structure substantially along theaxis of revolution, wherein re-directed radiation from the specimen isallowed into the annular meso-optic by the secondary optical structureif an angle of incidence of the re-directed radiation exceeds the angleof Total Internal Reflectance.

The foregoing is a summary and thus may contain simplifications,generalizations, and omissions of detail; consequently, those skilled inthe art will appreciate that the summary is illustrative only and is notintended to be in any way limiting.

For a better understanding of the embodiments, together with other andfurther features and advantages thereof, reference is made to thefollowing description, taken in conjunction with the accompanyingdrawings. The scope of the invention will be pointed out in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The same reference number represents the same element on all drawings.The drawings are not necessarily to scale.

FIG. 1 is an isometric view of an annular optical device according to anembodiment of the invention.

FIG. 2 is an end view of the annular optical device of FIG. 1.

FIG. 3 is a side view of the annular optical device.

FIG. 4 is a section view AA of the annular optical device along the axisof revolution A.

FIG. 5 shows the annular optical device according to another embodimentof the invention.

FIG. 6 is a section view BB of the annular optical device of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-6 and the following description depict specific examples toteach those skilled in the art how to make and use the best mode of theinvention. For the purpose of teaching inventive principles, someconventional aspects have been simplified or omitted. Those skilled inthe art will appreciate variations from these examples that fall withinthe scope of the invention. Those skilled in the art will appreciatethat the features described below can be combined in various ways toform multiple variations of the invention. As a result, the invention isnot limited to the specific examples described below, but only by theclaims and their equivalents.

FIG. 1 is an isometric view of an annular optical device 100 accordingto an embodiment of the invention. The annular optical device 100comprises an annular meso-optic 1 and a secondary optical structure 2that are substantially centered about an axis of revolution A. Theannular meso-optic 1 includes an annulus 11 that passes through theannular meso-optic 1 and is also substantially centered on the axis ofrevolution A (see FIG. 4). The secondary optical structure 2 resides inthe annulus 11 and as a result the secondary optical structure 2 issubstantially coaxial to the annular meso-optic 1. The secondary opticalstructure 2 may be positioned within the annulus 11 so that thesecondary optical structure 2 extends at least partially through theannular meso-optic 1 in some embodiments. The secondary opticalstructure 2 may be positioned to extend fully through the annulus 11 andthe annular meso-optic 1 in some embodiments.

The annular optical device 100 can comprise a component of an opticalinstrument. The annular optical device 100 can comprise a component ofany device that employs scattered, reflected, refracted, redirected, ortransmitted light (or other visible or invisible electromagneticradiation). As used herein, “re-directs” encompasses various mechanismsof light re-radiation including scattering, luminescing, refracting,etc.

The annular optical device 100 can comprise a component of any devicethat uses light to detect, measure, and/or characterize foreign matter,such as particulates, in a fluid. For example, the annular opticaldevice 100 can comprise a component of a device used to detect and/orquantify particulates in water. However, the fluid can comprise anymanner of gases or liquids and can comprise various combinations ofgases, liquids, and/or solids. The annular optical device 100 cancomprise a component of a turbidimeter or nephelometer in someembodiments.

The annular optical device 100 can receive light (or other radiation)directed along the axis of revolution A, into the secondary opticalstructure 2, wherein the annular optical device 100 captures only lightthat is substantially radially scattered within the secondary opticalstructure 2. The annular optical device 100 re-directs the scatteredlight back out, substantially parallel to the axis of revolution A andsubstantially opposite in direction to the impinging radiation. Theannular optical device 100 therefore re-directs the radiation as aplanar wave front. The annular meso-optic 1 of the embodiments hereincomprises an axicon. Axicons are optical elements that are useful inconverging optical radiation propagating as a planar wave front into alinear foci, or conversely, collimating a radially divergent linearsegment of optical radiation to a planar wave front. Specifically, anannular axicon performs the convergence or collimation about an axis ofrevolution wherein the axicon does not occupy the space along the lineof focus. Annular axicons are particularly useful wherein the line offocus or line of radial divergence is substantially perpendicular to theplanar wave front.

The secondary optical structure 2 and the annular meso-optic 1 areseparated by a media 12. Media 12 includes a media refractive index thatis lower than a secondary optical structure refractive index.

The secondary optical structure 2 comprises a container including anopen end 2 a, a wall 2 b, and a closed end 2 c in some embodiments. Insome embodiments, the secondary optical structure 2 includes aradiation-transmittable closed end 2 c that is configured tosubstantially admit impinging electromagnetic radiation. In someembodiments, the secondary optical structure 2 includes at least oneradiation-transmittable region in the wall 2 b and about and/or alongthe line of focus 7 of the annular meso-optic 1, with the at least oneradiation-transmittable region being configured to substantially passimpinging electromagnetic radiation. Alternatively, the entire secondaryoptical structure 2 can be substantially transmittable to radiation. Theradiation can travel out of the secondary optical structure 2 throughthe open end 2 a.

The secondary optical structure 2 can hold a specimen 3 to be tested,measured, or otherwise quantified. It should be understood that thespecimen 3 may be statically held within the secondary optical structure2 or may be circulated within or circulated through the secondaryoptical structure 2.

The secondary optical structure 2 is configured to hold a specimen to beradiated by impinging electromagnetic radiation directed into thesecondary optical structure 2 substantially along the axis of revolutionA. Radiation may be directed into the secondary optical structure 2,such as a beam of light 5, for example. The radiation may mainly passthrough the specimen 3 held in the secondary optical structure 2.However, at least some of the radiation may be scattered. The radiationmay be scattered by the specimen 3 (or scattered by components of ormaterials of interest within the specimen 3) as the radiation transitsthe secondary optical structure 2. The radiation may be scattered atdifferent angles.

The specimen 3 can comprise a gas, a liquid, or mixtures of gas, liquid,and/or solids. The specimen 3 may include particles of gas, liquid, orsolids that are desired to be detected and/or quantified. The specimen 3can include suspended particles or various mixtures, suspensions, orimmiscible materials.

Placement of the secondary optical structure 2 within the annulus of theannular axicon/meso-optic 1 creates an angular propagation limitationthat controls the propagation of radiation into the annular opticaldevice 100. Radiation that exceeds a condition for Total InternalReflection (TIR) is allowed to pass through the secondary opticalstructure 2 and propagate into the annular axicon. This is shown by theray 5 f in FIG. 4. However, radiation that is reflected due to TIRpropagates only within the secondary optical structure 2; i.e.,radiation within the secondary optical structure 2 is only allowed toexit dependent upon the angle of incidence of the radiation to theoptical surface of the secondary optical structure 2.

The secondary optical structure 2 is formed of a material such thatradiation impinging on the walls of the secondary optical structure 2 ata relatively low angle will be internally reflected, refracted, orotherwise re-directed. This is illustrated by rays 5 c and 5 d of FIG.4. If the angle of incidence is less than a predetermined incidencethreshold, then the scattered radiation is internally re-directed by thesecondary optical structure 2 and cannot pass into the annularmeso-optic 1.

The secondary optical structure 2 is positioned within the annulus 11such that a line of focus 7 of the annular meso-optic 1 is locatedwithin the secondary optical structure 2, and therefore is locatedwithin the specimen 3 contained in the secondary optical structure 2. Anoptical beam 5 (or other beam of suitable electromagnetic radiation) maybe projected along the axis of revolution A of the annular meso-optic 1,substantially along the line of focus 7. The measurement volume isdefined by the chord length of the line of focus 7 and by thecross-sectional area of the optical beam 5. As a consequence, radiationscattered by the specimen 3 in the region of the line of focus 7 mayleave the secondary optical structure 2 and enter the annular meso-optic1 (see the ray 5 f). The scattered radiation received in the annularmeso-optic 1 is substantially radially divergent from a line of focus 7of the annular meso-optic 1, regardless of an angular separation of theimpinging electromagnetic radiation from the axis of revolution A.However, the secondary optical structure 2 restricts the scatteredradiation and does not allow all scattered radiation to enter theannular meso-optic 1.

Scattered radiation from within the secondary optical structure 2 andwithin the annulus 11 of the annular meso-optic 1 is allowed into theannular meso-optic 1 by the secondary optical structure 2 if an angle ofincidence of scattered radiation exceeds a predetermined incidencethreshold. The annular meso-optic 1 re-directs the scattered radiationto comprise re-directed radiation that is substantially parallel to theaxis of revolution A and substantially opposite in direction to theimpinging electromagnetic radiation. The annular meso-optic may bepreferentially positioned so as to re-direct the scattered radiationsubstantially parallel to the axis of revolution A and substantially inthe same direction to the impinging electromagnetic radiation.

Therefore, scattered radiation that impinges on the wall of thesecondary optical structure 2 at a relatively high angle, i.e.,substantially radially, will not be internally re-directed and will exitthe secondary optical structure 2. Consequently, the scattered radiationmust be scattered substantially radially and substantiallyperpendicularly, i.e., at a high angle from the direction of theimpinging electromagnetic radiation. Further, if the scattered radiationis within the annulus 11 of the annular meso-optic 1, then the scatteredradiation will be re-directed by the annular meso-optic 1. In someembodiments, the scattered radiation must be scattered from within aspan denoted by the line of focus 7. The re-directed radiation exitsfrom the planar annular optical surface 1 d of the annular meso-optic 1.As a result, the re-directed radiation will be directed substantiallyparallel to the axis of revolution A. The re-directed radiation may besubstantially opposite in direction to the original, entering radiation.The re-directed radiation may comprise a substantially planar wavefront.

Radially scattered radiation outside of either the annulus 11 or theline of focus 7 will not enter the annular meso-optic 1. Radiallyscattered radiation outside of either the annulus 11 or the line offocus 7 will not be re-directed by the annular meso-optic 1. If theangle of incidence of the scattered radiation is less than thepredetermined incidence threshold, then the scattered radiation isinternally re-directed by the secondary optical structure 2 and cannotpass into the annular meso-optic.

Similarly, even if the angle of incidence of the scattered radiationexceeds the predetermined incidence threshold, but the scatteredradiation is scattered by the specimen in the region before the annularmeso-optic 1, such as a region within the radiation-blocking structure4, then the scattered radiation may still be prevented from leaving thesecondary optical structure 2. Ray 5 g propagates beyond the annularoptical arrangement through secondary optical structure 2 and does notcontribute to the measureable optical signal of interest. Ray 5 g doesnot generate optical noise and ray 5 g is considered to be loss.

The annular optical device 100 can further include a radiation-blockingstructure 4 positioned over or incorporated into at least a portion ofthe secondary optical structure 2, as shown, wherein theradiation-blocking structure 4 blocks radiation scattered beforeencountering the annular meso-optic 1 and therefore prevents suchscattered radiation from leaving the secondary optical structure 2. Theradiation-blocking structure 4 can be formed of any appropriateradiation-absorbing material. The radiation-blocking structure 4 can beformed of any appropriate radiation-reflecting material. Theradiation-blocking structure 4 can be formed of any appropriateradiation-impenetrable material.

The radiation-blocking structure 4 can be formed so as to fit over atleast a portion of the secondary optical structure 2, as shown. Theradiation-blocking structure 4 in some embodiments can extend at leastpartially out from the planar annular optical surface 1 d of the annularmeso-optic 1. As a result, radiation that is scattered substantiallyradially, but before the annulus 11, is blocked from leaving thesecondary optical structure 2. As a result, this scattered radiation istherefore blocked from entering the planar annular optical surface 1 dof the annular meso-optic 1. The radiation-blocking structure 4,comprising a radiation absorbing media, is located beyond the foci ofthe annular meso-optic 1.

In addition, the radiation-blocking structure 4 may provide a locatingor positioning function. The radiation-blocking structure 4 maysubstantially center the secondary optical structure 2 within theannulus 11 of the annular meso-optic 1. The radiation-blocking structure4 may create a desired size and uniformity of media 12 between theannular meso-optic 1 and the secondary optical structure 2.

FIG. 2 is an end view of the annular optical device 100 of FIG. 1. Fromthis view, it can be seen that the annular meso-optic 1, the secondaryoptical structure 2, and the radiation-blocking structure 4 may besubstantially coaxial. In some embodiments, the radiation-blockingstructure 4 positions the secondary optical structure 2 substantiallycoaxially within the annulus 11 of the annular meso-optic 1. Theradiation-blocking structure 4 prevents the outside surface of thesecondary optical structure 2 from direct contact with the annularmeso-optic 1 by centering the structure within the annulus of theannular meso-optic.

FIG. 3 is a side view of the annular optical device 100. In this figure,an optical beam 5 (or other radiation) is shown entering the closed end2 c of the secondary optical structure 2. In this embodiment, thesecondary optical structure 2 extends from either side of the annularmeso-optic 1, but it should be understood that the annular opticaldevice 100 may be formed in other configurations and with otherdimensions. The radiation-blocking structure 4 is located on thesecondary optical structure 2 on the side before the annular meso-optic1, i.e., between the source of the optical beam 5 and the annularmeso-optic 1.

FIG. 4 is a section view AA of the annular optical device 100 along theaxis of revolution A. The substantially hollow shape of the secondaryoptical structure 2 is shown in this section view. The solid shape ofthe annular meso-optic 1 and the annulus 11 therein are shown in thissection view. The substantially pentagonal cross-sectional shape of theannular meso-optic 1 of this embodiment is shown in this section view.

It can be seen that media 12 exists between the annular meso-optic 1 andthe secondary optical structure 2, specifically outside the wall 2 b ofthe secondary optical structure 2. Media 12 can comprise a media of airin some embodiments. Media 12, when comprised of air, will have a mediarefractive index that is lower than the refractive index of wall 2 b ofsecondary optical structure 2 (i.e., the secondary optical structurerefractive index).

However, it should be understood that media 12 may be comprised of anysuitable material that possesses an index of refraction lower than thewall 2 b of the secondary optical structure 2. As a result of the lowerindex of refraction of media 12, a boundary exists between the wall 2 bof the secondary optical structure 2 and the media 12 which will causescattered radiation to be refracted, reflected, or otherwise internallyre-directed by the secondary optical structure 2. If the scatteredradiation has an angle of incidence less than a predetermined incidencethreshold, then the scattered radiation will be re-directed and remainwithin the secondary optical structure 2. If the scattered radiationencounters the boundary with an angle of incidence greater than thepredetermined incidence threshold, then the scattered radiation will notbe re-directed and will exit the secondary optical structure 2 throughwall 2 b. Such high angle of incidence scattered radiation will besubstantially radial in direction with respect to the secondary opticalstructure 2 and the annular meso-optic 1.

The secondary optical structure 2 can be formed of a suitable materialor materials. The secondary optical structure 2 may be entirelytransmittable to impinging radiation or may include windows or regionsthat are transmittable or semi-transmittable to radiation within anotherwise radiation-absorbing structure. The secondary optical structure2 may include at least one radiation-transmittable region about the lineof focus 7 of the annular meso-optic 1. The secondary optical structure2 may include a radiation-transmittable closed end 2 c that isconfigured to admit impinging electromagnetic radiation.Radiation-transmittable regions may be of different material, ofdifferent refractive index, or of different optical opacity. Thesecondary optical structure 2 is shown as comprising a substantiallycylindrical container. However, the secondary optical structure 2 can beformed of other shapes, as desired.

The annular meso-optic 1 and the secondary optical structure 2 maycomprise a portion of an instrument that quantifies particles in aspecimen 3 by quantifying the scattering of impinging radiation. In someembodiments, the impinging radiation comprises visible or non-visiblelight. However, electromagnetic radiation of other wavelengths may alsobe employed.

The annular optical arrangement 100 provides utility in convergingradiation from a substantially planar wave to a line of focus.Conversely, the annular optical arrangement 100 is capable ofcollimating a radially divergent linear segment of radiation to asubstantially planar wave while advantageously restricting the amount ofradiation not associated with the primary ray path of the opticalarrangement from propagating out of the annular optical arrangement 100.

The annular meso-optic 1 of the embodiment shown comprises a solidannular meso-optic 1. The meso-optic is preferentially a solid ofrevolution about the axis of revolution A. The cross-sectional shape ispreferentially that of pentagon which forms a cylindrical opticalsurface 1 a parallel to the axis of revolution and a planar annularoptical surface 1 d that is substantially perpendicular to the axis ofrevolution. An inner annulus of the planar annular optical surface 1 dis coincident with the cylindrical optical surface 1 a. Optical surfaces1 b and 1 c are substantially conical with respect to the axis ofrevolution A and are convergent to a circular intersection at a distanceradial to the axis of revolution. The conical optical surfaces 1 b and 1c are preferentially coated to reflect radiation impingent upon theinternal optical surfaces. In addition, the conical optical surface 1 bis coincident to the outer annulus of the planar annular optical surface1 d and the conical optical surface 1 c is coincident to the end of thecylindrical optical surface 1 a opposite the planar annular opticalsurface 1 d. Non-optical conical surface 1 e terminates the convergenceof conical optical surfaces 1 b and 1 c at a chord length along the axisof revolution not less than the length of the cylindrical opticalsurface 1 a so as to reduce the cost of fabrication and fragility of themeso-optic element without vignette of the annular optical arrangement.The non-optical conical surface 1 e is preferentially inclined about 45degrees to the axis of revolution. The conical optical surfaces 1 b and1 c are inclined relative to the axis of revolution so as to reflect orredirect radiation that is substantially perpendicularly radiallydivergent from the line of focus 7 to be substantially parallel to theline of focus 7. Conversely, the annular meso-optic 1 can redirectradiation that is traveling substantially parallel to the line of focus7 to be substantially radially impinging on the line of focus 7 in theregion of the cylindrical optical surface 1 a.

An annular meso-optic as described possessing pentagonal cross-sectionalannular volume of revolution converges planar waves of electromagneticradiation to line of focus 7 substantially perpendicular to planar wavepropagation or collimates optical radiation emitted radially divergentfrom line of focus 7 substantially perpendicular from the radialemission regardless of modest error in alignment of the annularpentagonal meso-optic axis of revolution to line of focus 7; such as amodest error in alignment of several degrees, for example.

It should be noted that annular meso-optic 1 need not be solidconstruction nor of pentagonal cross-sectional shape. Indeed, otherconic surface(s) comprised of first-surface reflecting, refracting ordiffractive surfaces can be used in the construction of an annularmeso-optic in which the line of focus 7 is substantially coincident tothe axis of revolution of the meso-optic.

In addition to the shown components and structures, any manner ofadditional lenses, components, and/or surfaces may be included in orderto direct, collimate, disperse, condense, focus, magnify, and/orde-magnify the radiation. Additional components may be located before orafter the annular optical device 100. For example, the annular opticaldevice 100 may include a light or radiation source adjacent to andconfigured to direct radiation into the secondary optical structure 2.Further, a radiation detector may be positioned adjacent to the planarannular optical surface 1 d of the annular meso-optic 1 in order toreceive and quantify the radiation re-directed by the annular meso-optic1 and exiting from the planar annular optical surface 1 d.

It is obvious to those skilled in the art of optics, physics orelectromagnetic theory that planar or spherical propagating waves ofoptical radiation may be manipulated by absorptive, refractive,diffractive and reflective elements alone or by incorporation with theannular optical device in order to collimate, magnify, de-magnify,disperse, condense, or bring to focus said radiation.

The solid annular meso-optic substrate material of the preferredembodiment may be that of any material transmittable to the radiation ofinterest. For example, in the visible electromagnetic spectrum, theimpinging radiation may comprise electromagnetic radiation betweenapproximately 380 nanometer (nm) to 780 nm, i.e., visible light asdefined by the Commission internationale de l′eclairage (CIE). Thesubstrate material may be that of Schott Glass N-BAK4, N-BK7, PMMA, orany other optically transmittable material. Further, the reflectivecoating on the conical optical surfaces 1 b and 1 c may be that of gold,silver, aluminum, or any other material reflective in the visiblespectrum. In addition, the non-optical conical surface 1 e may be coatedwith a light absorptive material such as black paint. The opticalsurfaces 1 a and 1 d may be uncoated or may be coated to reducereflection loss at the wavelength(s) of interest. For applications inthe visible wavelength range, an anti-reflective coating(s) may be thatof an about quarter-wavelength thickness of magnesium fluoride (MgF2)applied to the transmittable optical surfaces 1 a and 1 d.

In one example, given an optical beam 5 of wavelength 0.5875618micrometer (um) (i.e., the Fraunhofer ‘d’ helium emission wavelength)propagating in a surrounding media, like that of air, of refractiveindex 1.0000 along the line of focus 7 in a direction so as to enter theplanar surface of the glass vial of refractive index 1.5168 into aspecimen of refractive index 1.3330 into outside surfaces 2 b of thevial also residing in the surrounding media. By Snell's Law ofrefraction, any redirection of optical beam 5 due to scatter or otheroptical phenomenon results in TIR if the angle of incidence to theinside wall 2 a of the vial is greater than or equal to about 48.6degrees, as measured from the normal or perpendicular to the axis ofrevolution of the cylindrical surface, as in rays 5 c and 5 d.

FIG. 5 shows the annular optical device 100 according to anotherembodiment of the invention. In this embodiment, the annular meso-optic9 comprises a substantially triangular cross section of rotation,specifically a solid-of-revolution of a right angle triangle is shown.The triangular annular meso-optic 9 of this embodiment advantageouslyhas one less optical surface to fabricate, features a shorter ray path,and requires less material. Along the axis of revolution of the annulusof the annular meso-optic 9 is the secondary optical structure 2. Thesecondary optical structure 2 and specimen 3 are coaxial to thetriangular annular meso-optic 9. The previous discussion of thepropagation of the radiation beam 5 and the rays 5 a, 5 b, 5 c, 5 d, 5e, 5 f and 5 g is likewise applicable to this embodiment.

FIG. 6 is a cross-section view BB of the annular optical device 100 ofFIG. 5. In the figure, a conical optical surface 9 b of the triangularannular meso-optic 9 is inclined relative to the axis of revolution A soas to reflect any radiation that is substantially perpendicularlyradially divergent from the line of focus 7. The conical optical surface9 b redirects the radiation in a direction substantially parallel to theline of focus 7. The inner annulus of a planar annular optical surface 9c and a cylindrical optical surface 9 a are coincident at one end of thecylindrical optical surface 9 a. The conical optical surface 9 b iscoincident to an outer annulus of the planar annular optical surface 9 cand is coincident to the cylindrical optical surface 9 a at the end ofcylindrical optical surface 9 a that is opposite to the planar annularoptical surface 9 c. As in other embodiments, the conical opticalsurface 9 b may be coated to reflect impinging radiation. The opticalsurfaces 9 a and 9 c may be discretionarily uncoated to reduce cost orcoated to reduce reflection loss at the wavelength(s) of interest.

The disclosed annular optical device is not limited to the examplespresented herein. Annular meso-optics comprising one or more conicaloptical surfaces may be used. Annular meso-optics with internallyreflecting surface(s) or externally reflecting surface(s) may be used.It is further understood that the annular optical device may be formedby approximation of the conic optical surfaces using multiple radiallysegmented planar surfaces. In addition, variation in the cross-sectionalcurvature(s) of the surfaces of revolution may also be practiced bymodification of one or more of the disclosed optical surfaces to opticalsurfaces that are substantially spherical, ellipsoidal, parabolic, orhyperbolic.

The annular optical device 100 may find use in the fields of, forexample, fluorometry, flow cytometry, illuminators, laser optics,electromagnetic concentrators, flow metrology, nephelometry, andparticle analysis. However, this listing is not exhaustive. It should beunderstood that other uses are contemplated and are within the scope ofthe description and claims.

The detailed descriptions of the above embodiments are not exhaustivedescriptions of all embodiments contemplated by the inventors to bewithin the scope of the invention. Indeed, persons skilled in the artwill recognize that certain elements of the above-described embodimentsmay variously be combined or eliminated to create further embodiments,and such further embodiments fall within the scope and teachings of theinvention. It will also be apparent to those of ordinary skill in theart that the above-described embodiments may be combined in whole or inpart to create additional embodiments within the scope and teachings ofthe invention. Accordingly, the scope of the invention should bedetermined from the following claims.

What is claimed is:
 1. An annular optical device (100), comprising: a.an annular meso-optic (1) including an annulus (11) centered about anaxis of revolution (A); and b. a secondary optical structure (2)substantially coaxial within the annulus (11) of the annular meso-optic(1), wherein the secondary optical structure (2) and the annularmeso-optic (1) are separated by a media (12) comprising a mediarefractive index that is lower than a secondary optical structurerefractive index, with the secondary optical structure (2) beingconfigured to hold a specimen to be radiated by impingingelectromagnetic radiation directed into the secondary optical structure(2) substantially along the axis of revolution (A), wherein re-directedradiation from the specimen is allowed into the annular meso-optic (1)by the secondary optical structure (2) if an angle of incidence of there-directed radiation exceeds the angle of Total Internal Reflectance.2. The annular optical device of claim 1 wherein after re-directedradiation is allowed into the annular meso-optic (1) it reflects theradiation so that it is substantially parallel to the axis of revolution(A).
 3. The annular optical device of claim 1 wherein the re-directedradiation is selected from the group consisting of the scatter,luminescence, reflectance and refraction of radiation.
 4. The annularoptical device (100) of claim 1, wherein the re-directed radiationreceived in the annular meso-optic (1) is substantially radiallydivergent from a line of focus (7) of the annular meso-optic (1),regardless of an angular separation of the impinging electromagneticradiation from the axis of revolution (A).
 5. The annular optical device(100) of claim 1, wherein the re-directed radiation is received by theannular meso-optic (1) and reflected substantially along the axis ofrevolution (A), wherein reflected radiation exits from a planar annularoptical surface (1 d) of the annular meso-optic (1).
 6. The annularoptical device (100) of claim 1, wherein if the angle of incidence isless than the angle of Total Internal Reflectance, then the re-directedradiation is internally reflected by the secondary optical structure (2)and cannot pass into the annular meso-optic (1).
 7. The annular opticaldevice (100) of claim 1, with the secondary optical structure (2)including a radiation-transmittable closed end (2 c) that is configuredto admit the impinging electromagnetic radiation.
 8. The annular opticaldevice (100) of claim 1, with the secondary optical structure (2)including at least one radiation-transmittable region about the line offocus (7) of the annular meso-optic (1).
 9. The annular optical device(100) of claim 1, further comprising a radiation-blocking structure (4)positioned over or incorporated into at least a portion of the secondaryoptical structure (2), wherein the radiation-blocking structure (4)prevents radiation from leaving the secondary optical structure (2). 10.The annular optical device (100) of claim 1, further comprising aradiation-blocking structure (4) positioned over or incorporated into atleast a portion of the secondary optical structure (2) and extending atleast partially out from a planar annular optical surface (1 d) of theannular meso-optic (1).
 11. The annular optical device (100) of claim 1,further comprising a radiation-blocking structure (4) positioned over orincorporated into at least a portion of the secondary optical structure(2) and substantially centering the secondary optical structure (2)within the annulus (11) of the annular meso-optic (1).
 12. A method offorming an annular optical device, the method comprising: a. providingan annular meso-optic including an annulus centered about an axis ofrevolution; and b. providing a secondary optical structure substantiallycoaxial within the annulus of the annular meso-optic, wherein thesecondary optical structure and the annular meso-optic are separated bya media having a media refractive index that is lower than therefractive index of the secondary optical structure, with the secondaryoptical structure being configured to hold a specimen to be radiated byimpinging electromagnetic radiation directed into the secondary opticalstructure substantially along the axis of revolution, whereinre-directed radiation from the specimen is allowed into the annularmeso-optic by the secondary optical structure if an angle of incidenceof the re-directed radiation exceeds the angle of Total InternalReflectance.
 13. The method of claim 12 wherein after re-directedradiation is allowed into the annular meso-optic (1) it reflects theradiation so that it is substantially parallel to the axis of revolution(A).
 14. The method of claim 12 wherein the re-directed radiation isselected from the group consisting of the scatter, luminescence,reflectance and refraction of radiation.
 15. The method of claim 12,wherein the re-directed radiation received in the annular meso-optic issubstantially radially divergent from a line of focus of the annularmeso-optic, regardless of an angular separation of the impingingelectromagnetic radiation from the axis of revolution.
 16. The method ofclaim 12, wherein the re-directed radiation is received by the annularmeso-optic and reflected substantially along the axis of revolution,wherein re-directed radiation exits from a planar annular opticalsurface of the annular meso-optic.
 17. The method of claim 12, whereinif the angle of incidence is less than the angle of Total InternalReflectance, then the re-directed radiation is internally reflected bythe secondary optical structure and cannot pass into the annularmeso-optic.
 18. The method of claim 12, with the secondary opticalstructure including a radiation-transmittable closed end that isconfigured to admit the impinging electromagnetic radiation.
 19. Themethod of claim 12, with the secondary optical structure including atleast one radiation-transmittable region about the line of focus of theannular meso-optic.
 20. The method of claim 12, further comprisingproviding a radiation-absorbing structure positioned over orincorporated into at least a portion of the secondary optical structure,wherein the radiation-blocking structure prevents radiation from leavingthe secondary optical structure.
 21. The method of claim 12, furthercomprising providing a radiation-absorbing structure positioned over orincorporated into at least a portion of the secondary optical structureand extending at least partially out from a planar annular opticalsurface of the annular meso-optic.
 22. The method of claim 12, furthercomprising providing a radiation-absorbing structure positioned over orincorporated into at least a portion of the secondary optical structureand substantially centering the secondary optical structure within theannulus of the annular meso-optic.